New indazolotriazolyl stilbene brighteners soluble in organic media



United rates This invention relates to new stilbene triaZole derivativesfor use as optical bleaching agents in synthetic resins and otherorganic materials More particularly, it relates to compounds of theformula in which R is hydrogen, chloro, bromo or lower alkyl.

The use and mode of action of brighteners or optical bleaching agents inthe textile field is well known- A large market has developed with suchagents. However, because of their properties (especially solubility andlight fastness) the agents used in the textile field are not suitablefor general use in organic systems, especially in polymeric plasticcompositions and in fats, oils and waxes and the like. In suchcompositions there is a definite need for agents which will brighten theclarity and overcome a dull appearance or yellow color. Thus, in thecase of plastics, such agents would increase the clarity of transparentplastics, the whiteness of opaque plastics which have been loaded withwhite pigment and the brightness of colored plastics of pastel shades.It is Well known,

. furthermore, that certain plastics such as cellulose acetate andpolyvinyl chloride normally have a yellow tinge when first prepared andwould therefore profit by the inclusion of such agents.

One of the more important classes of textile brighteners is that of themonotriazolyl stilbene derivatives. A number of derivatives of such aring structure have been described as the optical bleaching agents forcloth. There has also been recently described an optical bleaching agentfor plastics, of the triazolyl stilbene structure, in which the sulfonicacid groups of the textile brightener are converted into ester or amidegroups. These however, have not proved to be fully satisfactory sincethey are found to be quite weak in fluorescence.

I have found that certain triazolyl stilbene brighteners having specificsubstituents in specific places in the molecule, completely lacking anysulfonic acid substituent, are excellent brightener for resins, oils,fats, waxes and the like. This new class of brighteners of my inventionare much stronger as brighteners for plastics than the heretofore knownsulfonic ester and sulfonamide derivatives of triazolyl stilbenecompounds. The class of compounds which fall within the scope of myinvention comprise compounds of the formula in which R is hydrogen,chloro, bromo or lower alkyl. Especially preferred is the compound3,062,814 Fatented Nov. 6, '1 962 The compounds of my invention can beprepared by a number of methods. The most convenient method involves thediazotization of a 4-aminostilbene or the proper 4-aminostilbenederivative and coupling the diazo into an aminoindazole of the properstructure, followed by oxidation of the o-aminoazo compound to4-triazole. This synthesis can be illustrated by the following equation.

Stilbenes which may be used in the synthesis of the compounds of myinvention include the following 4-aminostilbene4-amino-2'-chlorostilbene 4-amino-3 '-chlorostilbene4-amino-4-chlorostilbene 4-amino-2'-methylstilbene 4-arnino-3'-methylstilbene 4-amino-4'-methylstilbene 4-amino-2'-bromostilbene4-amino-3'-bromostilbene 4-amino-4'-bromostilbene4-amino-2'-ethylstilbene 4-amino-2-butylstilbene4-amino-4'-propylstilbene 4-amino-3 '-methylstilbene The couplingcomponent in the synthesis of the compounds of my invention isS-aminoindazole.

The compounds of the invention, because of their blue fiuoroescenceeffects may be used as optical bleaching agents for a variety of organicsystems. Thus, because of their desirable solubility, fluoroescenceeffects, and light stability, they can be used as fluorescent agents forlubricating oils, Waxes, fats, etc.; for brightening agents,

ever, the preferred amount depends on the particular brightener used andits substrate. At too low a concentration no effect is observed. At toohigh a concentration quenching of fluorescence occurs. Thus, thecompound of the formula is effective in polystyrene at 0.005% butquenches at 0.05%.

This application is a division of my copending application, Serial No.798,604, filed March 11, 1959, now abandoned.

My invention can be illustrated by the following examples in which partsare by weight unless otherwise specified.

Example 1 NH CH A diazo solution is formed from 1.95 parts of 4-aminostilbene in acetic acid and this is added with stirring to 1.4parts of S-aminoindazole dissolved in 50 parts of water containing about3 parts of hydrochloric acid and about 50 parts of a saturated aqueoussolution of sodium acetate. The coupling proceeds rapidly and afterstirring for a short time the solid material is removed by filtration,washer with water and dried.

The aminoazo compound is then added to a mixture of 50 parts pyridine,7.5 parts of 95% ethanol and parts of water. The mixture is heated withstirring and to it is added a solution of 12 parts of copper sulfatepentahydrate, 50 parts of water and parts of concentrated aqueousammonium hydroxide. After heating at reflux until triazolization iscomplete the solid material is removed by filtration and washed withwater. It is purified by extraction with dilute hydrochloric acid andcrystallization from pyridine solution and reprecipitation from analkaline ethanol solution.

The product, obtained in the form of a tan solid, dissolves in organicsolvents, such as pyridine, ethanol and dimethylformamide to givestrongly fluorescent solutions.

Similar products containing substituents are obtained by following thesame procedure, replacing the 4-aminostilbene with4-amino-2'-chlorostilbene, 4-amino-3- methylstilbene,4-amino-4'-bromostilbene, 4-amino-2'- ethylstilbene,4-amino-2-bromostilbene and 4-amino-4- chlorostilbene. The productsobtained are those having the indicated substituents in the stilbeneportion of the molecule.

Example 2 To 100 parts polystyrene heated to fusion on a 2-roller Throppmill is added 0.005 part of the product of Example l. The blend ismilled in 75 passes at about 340 F., then moled into chips 2" x 5" x0.05". The chips Show intense blue fluorescence under ultraviolet light,and

it when viewed by daylight show an attractive white transparency, whichcontrasts with the grayish appearance of similar polystyrene chips notcontaining the brlghtener.

Example 3 A blend of parts polystyrene, 0.2 part titanium dioxide(rutile crystals), and 0.005 part of the product of Example 1 is milledin the Thropp mill as in the previous example, and molded into chips.The chips fluoresce intensely under ultraviolet light, and show a clearwhite opacity by daylight, in marked contrast to the grayish appearanceof chips prepared without the brightener.

Example 4 A mixture of 100 parts vinyl chloride homopolymer, 50 partsdioctyl phthalate, 2 parts barium-cadmium laurate, and 1 part triarylphosphite is milled in a Thropp mill at 340-350 C. till fused, whereupon0.005 part of the product of Example 1 is added and the blend furthermilled in 40 passes with heating, and molded into sheeting. The sheetshows a blue fluorescence in ultraviolet light, and is relatively whitein daylight as compared to the normal yellow hue of polyvinyl chloridesheeting prepared without addition of the brightener.

Example 5 To 100 parts of high-pressure (low density) polyethylene resinfused in a Thropp mill is added 0.005 part of the product of Example 1.The milling is continued at 340 F. in 40 passes. The films molded fromthis blend have a white translucent appearance which is brighter thanthat of a control film prepared Without the brightener.

If in place of the above resin, cellulose acetate polymer is used andblended with the brightener, the resulting film is similarly brighterthan a control film.

I claim:

1. A compound of the formula in which R is selected from the groupconsisting of hydrogen, chloro, bromo and lower alkyl.

2. The compound of the formula References Cited in the file of thispatent FOREIGN PATENTS 200,143 Austria Oct. 25, 1958 1,183,142 FranceJan. 26, 1959 1,199,528 France June 22, 1959 560,579 Belgium Mar. 5,1958 560,848 Belgium Oct. 15, 1957 565,237 Belgium Mar. 15, 1958

1. A COMPOUND OF THE FORMULA